Heat pumps sometimes operate in conditions of freezing precipitation such as freezing rain, snow, sleet, hail, and the like. Most heat pumps use a top discharge fan system located outdoors. The air leaving the heat pump, through the fan, orifice ring and grill, has been chilled below the ambient temperature. Freezing precipitation can form ice in the fan system and impair operation of the fan and the heat pump. Although the fan and heat pump may continue to operate, objectionable noise may occur as a result of ice buildup and ice-bridging. As a result, HVAC service personnel are often called to service the heat pump on the perception that the heat pump is not functioning properly. Further, if enough ice buildup occurs, the unit may experience a reduced airflow or complete loss of airflow causing the heat pump to operate at a reduced output and heating efficiency.